The galvanic cell has become a primary power source for many portable electronic devices such as tape recorders, portable telephones, lanterns, radios and the like. In order to maintain the overall electronic devices as compact as possible, the electronic devices are usually designed with cavities to accommodate batteries as their power source. The cavities are usually made so that a battery can be snugly positioned therein, thus making electronic contact with appropriate terminals within the device. To accommodate the electronic component manufacturers, the battery industry has adapted several conventional size cells which the manufacturers can rely upon in designing their devices which require portable power sources. Due to the large number of battery-powered devices on the market, there has been a demand for increased power output capacities of standard size cells. Accordingly, various cell constructions have been employed so as to provide a sufficient output capacity. For example, cells with coiled electrode assemblies (jellyroll construction) have been used to increase the interfacial area contact between the active cell components. Use of coiled electrodes serves to decrease the cell's internal resistance and thereby increase the maximum possible drain rates. Cells that incorporate a jellyroll construction are widely known in the battery art and usually involve placement of the coiled electrode in a composite housing which serves as the current conductive terminals for the cell. In such structures, the electrode of one polarity can be electrically connected to a conductive housing portion, and the electrode of the opposite polarity can be generally electrically connected to another conductive housing portion which is insulated relative to the electrically conductive first-mentioned housing portion. The electrical contact between each electrode and its respective housing portion is generally formed by an elongated flexible electrically conductive connecting tab (current collector tab) or element which is secured at one end to the electrode and at the other end is secured to the respective housing portion. The current collector tabs are generally attached to the electrodes or electrode carriers, by welding pressure contact or other conventional means. This technique requires time-consuming manual operations in the cell assembly process which serve to reduce line productivity and add to the manufacturing costs. For example, some of the problems associated with using this method of tabbing are: (1) the obvious difficulty of handling and welding narrow strips of metal within the configured space of the cell; (2) dedicating a disproportionate percentage of the volume within the cell to accommodate the tab and assembly process; and (3) the tab is connected to the electrode in only one spot and therefore it is possible that any bulging of the cell could break the weld causing an open circuit; and (4) coil insertion is difficult due to the ease with which the electrodes and/or separator may by damaged.
U.S. Pat. No. 4,332,867 discloses a cell utilizing a coil assembly formed by winding negative and positive plates together with at least one separator therebetween. Each of the positive and negative plates is constituted by a main portion containing battery active materials and an edge portion free of the active material. In the coil assembly, the edge portions of the respective plates protrude outwardly beyond the opposite edges of the separator and are positioned on respective sides of the coil assembly. Positive and negative current collectors are made of a holeless nickel-plated steel sheet and welded to the edge portions of the respective plates by means of a plurality of welds. Although this type of cell construction provides a plurality of weld connectors to the electrode, it is possible that internal pressure buildup would cause the container to bulge thereby stressing the welds and eventually breaking the contact.
It is an object of the present invention to provide a coiled electrode assembly cell construction that can accommodate internal pressure buildup and bulging of the terminal cover without disrupting the electronic continuity between the terminal and one of the cell's electrodes.
Another object of the present invention is to provide a coiled electrode assembly cell construction with a telescopic tab secured to a terminal cover and one of the cell's electrodes and adapted to flex upon bulging of the cell without disturbing the electronic continuity of the cell.
Another object of the invention is to provide a coiled electrode cell construction that employs a telescopic type tab which can follow the edge of an unevenly wound electrode protruding from the coiled assembly and which is electronically secured to the edge of the electrode so that it can accommodate a degree of bulge without disrupting the electronic circuit of the cell.
The foregoing and additional objects will become fully apparent from the following description and the accompanying drawings.